Due to the environment changes, Governments of the industrialized countries are inclined to apply more restricted rules on fuel powered vehicles, and mostly transportation trucks. For instance, non-idling laws are coming into force, whereby, heavy trucks are not allowed to keep the engine running when the truck is not moving.
Depending on the laws of each country or state, each driver is required by law to rest for an average of 10 hours after driving for 14 hours, and virtually most of the electrical appliances used at home are also used in the cabin of the truck especially in heavy-duty trucks, in which, drivers often spend weeks on the road transporting goods.
Accordingly, truck drivers are forced to look for other alternatives in order to power the refrigeration unit and the cabin of the trailer when the truck is parked for maintenance or when the driver is resting. These alternatives include an external power source if the truck is parked in a parking that provides this facility, or a bank of batteries which charges when the main engine of the truck is on and enables for few hours of non-idling power, or a combustion engine with an alternator which provides DC power.
DC Appliances are very expensive and at the same time known to have a more frequent failure and breakdown. Additionally, the provision of DC power to the cabin for all the appliances requires large diameter cables which are expansive and subject to stealing especially when the driver parks the truck and rests in the cabin.
Several attempts have been made in the past for providing the cabin of the truck with a source of power that enable AC appliances in the cabin to function, such as televisions, fridges, microwaves etc.
FIG. 1 illustrates a conventional system for providing AC power to the cabin of a truck as published on the following website http://www.oksolar.com/inverters/truck_inverters.htm. The system includes a bank of batteries which are connected to the alternator of a truck for charging when the truck's engine is on. An inverter is then used for inverting the DC power to an AC power for powering the AC appliances in the cabin of the truck. The problem with this design is the short period of non-idling power, depending on the number of appliances being used in the cabin and the amount of power consumed thereby, in addition to the external load created on the alternator of the truck.
Another system marketed under the name COMFORTPRO™ provides an auxiliary power unit with DELTEK™ diesel-electric technology which runs of the truck's fuel supply and powers the cab accessories directly. This system is also expansive and complicated, and requires substantial changes in the pre-existing heating and cooling system of the truck cabin. Similar alternatives and auxiliary power units which require additional combustion engines are disclosed in the following websites:
www.tempastart.com
www.autothermusa.com
www.nitesystem.com
www.saferco.com
www.espar.com
www.auxgenerators.com
www.auxiliarypowerdynamics.com
www.rigmasterpower.com
www.trucktrailer.carrier.com
Furthermore, U.S. Pat. No. 6,232,679 describes a combined heat and electricity generating unit that is suitable for use in class 8 trucks and the like. When it is operating it provides heat for keeping the engine and cabin warm and electricity for use by the electricity consuming devices in the cabin.
Therefore, there has been a need for a simple, economic and at the same time environment friendly back-up system for providing A/C power to the cabin of a truck.